Oil Hydraulic System Research Articles

About Inverse Laplace Transform of a Dynamic Viscosity Function.

A dynamic viscosity function plays an important role in water hammer modeling. It is responsible for dispersion and decay of pressure and velocity histories. In this paper, a novel method for inverse Laplace transform of this complicated function being the square root of the ratio of Bessel functions of zero and second order is presented. The obtained time domain solutions are dependent on infinite exponential series and Calogero–Ahmed summation formulas. Both of these functions are based on zeros of Bessel functions. An analytical inverse will help in the near future to derive a complete analytical solution of this unsolved mathematical problem concerning the water hammer phenomenon. One can next present a simplified approximate form of this solution. It will allow us to correctly simulate water hammer events in large ranges of water hammer number, e.g., in oil–hydraulic systems. A complete analytical solution is essential to prevent pipeline failures while still designing the pipe network, as well as to monitor sensitive sections of hydraulic systems on a continuous basis (e.g., against possible overpressures, cavitation, and leaks that may occur). The presented solution has a high mathematical value because the inverse Laplace transforms of square roots from the ratios of other Bessel functions can be found in a similar way.

Finite Element Analysis of Butterfly Valve

The main objective of this project is shape optimization and structural stability of the butterfly valve for metallic and non-metallic materials butterfly valve is mostly used in the engine carburettors need to make structural stability and shape optimization plays the main role for this component, design modifications and material comparative analysis done in ANSYS Structural modules and find the optimized shape through stress, strain and deformation results. Valves for hydro power projects are installed for safety, maintenance, and shut-off, as well as for flow and pressure regulation. A Butterfly valve is a type of flow control device, which is widely used to regulate a fluid flowing through a section of pipe. This type of valve is mainly used as safety valve, turbine inlet valve, and pump valve for low to medium design pressures. They are operated by oil hydraulic systems for opening and closing or by closing weight and hydraulic pressure for opening. For turbine inlet valves, oil pressure can also be taken from the governor hydraulic oil system. The sealing system is of flexible, adjustable rubber/metal type to reduce leakage to a minimum. Water flow through the valve is possible in both directions. The main objective of this thesis work is to analyses the option of fabricated variant for door & body in place of casted, reduction in the material of valve body & door by structural design & FEM analysis & optimization in the material of valve component. The 3D modelling to be performs for butterfly valve by using CAD software. Further the stress & displacement FEM analysis of the butterfly valve to be performed by using ANSYS tool to evaluate the optimized result.

High-Speed Imaging of Water Hammer Cavitation in Oil–Hydraulic Pipe Flow

A pipe water hammer with column separation was studied in a range of flow rates (Re=465 to 2239) in a test rig with an acrylic glass observation section. Pressure transients were measured with piezoresistive pressure sensors, while the gas evaporation and condensation were captured by high-speed recording with a Photron SA-Z at a frame rate of 75,000 fps. Separation lengths were estimated by a threshold value in the images. The results did not show a sharp gas–oil interface but consisted of small, dispersed bubbles mixed with larger vapor structures, where the bubbles seemed to become smaller after each collapse. These findings differ from the transient cavitating characteristics commonly reported in nonhydraulic piping systems governed by different fluid properties and time scales. Good repeatability, both in terms of pressure transients and bubble distribution, was observed. The column separation was quantified as a metric of separation length, which was consistent between the tests. Combined with pressure measurements, these results may assist in obtaining a better understanding of the transient cavitation dynamics within oil–hydraulic systems as well as be used to improve modelling strategies towards more accurate cavitation erosion predictions.

Experimental Analysis of Flow Through Throttle Valve During Gaseous Cavitation

The multiphase flow in oil hydraulic systems has a very significant effect on the correct operation of the hydraulic system. Air can be found in various states in hydraulic systems, while free entrained air in the form of bubbles has the potential to be the most problematic. It especially affects the compressibility of the hydraulic liquid resulting in reduced stiffness of the hydraulic system. The actuators of the hydraulic mechanisms then do not achieve the fast response and the precision of movements depending on the input control signals. One possibility for the contamination of hydraulic fluid by air bubbles is through a phenomenon known as gaseous cavitation. This is a phenomenon in which gas is released when the pressure drops below the saturation pressure of the dissolved gas in the liquid. This article focuses on the experimental analysis of the flow through the throttle valve which is affected by the formation of air bubbles at the throttle edge of the valve. The regions of gaseous cavitation were observed at the different flow cross-section of the throttle valve. The throttle valve was placed into the block of transparent material to provide visualization of the individual measurements. The article is supplemented with photographs of the individual measurements showing the gaseous cavitation inception. Research background: flow cross-section, cavitation phenomenon, discharge coefficient. Purpose of the article: Effect of flow cross-section size and flow velocity on cavitation development. Methods: Experimental measurements. Findings & Value added: The investigation of the gaseous cavitation inception, Visualization of the individual measurements.

Influence of process parameters on laser beam machining of leather for oil hydraulic system application

Laser Beam Machining (LBM) is an unconventional process where the laser beam is directed to the work piece where the thermal energy is utilized to remove the material. Laser Beam Machining (LBM) is best suited for machining tough to cut material like leather as it provides several advantages like high precision, and no tool wear as there is no contact between work piece and nozzle. Leather seals are used in oil hydraulic systems. The laser beam machining was carried out for leather with different levels of process parameters like Power (P), Transverse Speed (Sp), Standoff Distance (SOD) and Gas Pressure (G.Pr) and its effect on various response parameters such as MRR, Conicity, Overcut and Circularity are studied. From the results obtained, out of two trials conducted on leather the second trial has high MRR, better overcut and circularity because of the fact that second trial has lesser SOD so the intensity is more and beam divergence is less compared to trial one. The most influential parameter for leather is transverse speed because the heat transfer on the workpiece gets changed with respect to time available for the heat to spread.

Oil-hydraulic power take-off concept for an oscillating wave surge converter

Abstract A power take-off oil-hydraulic system is designed for an oscillating wave surge converter. The adaptation of the converter to the power take-off is performed with genetic algorithms in order to find out the optimal geometrical and control parameters, while different power take-off layout configurations are simulated to maximize their efficiency. The simulations show that the power take-off of the oscillating wave surge converter is more effective and efficient, because the converter is driven by bigger excitation wave moments, rather than the resonant characteristics of the point absorber converter, and on the other hand, allows a less constrained design optimization of the mechanical interface with the power take-off. It was verified that these key features allow the production of lower oil flowrates at higher pressure levels, lower oil flow speeds at the cylinder ports and lower ratios between hydraulic peak and averaged power, thus characteristics that must be found in an efficient and effective power take-off.

Proposal of a Component to Restrict Dust from Entering an Oil Hydraulic System through an Oil Hydraulic Cylinder

Proposal of a Component to Restrict Dust from Entering an Oil Hydraulic System through an Oil Hydraulic Cylinder

Evaluation of Operability Performance in Oil Hydraulic Teleoperation System over IP Network

Evaluation of Operability Performance in Oil Hydraulic Teleoperation System over IP Network

Development of Oil Hydraulic Teleoperation System over IP Network

Development of Oil Hydraulic Teleoperation System over IP Network

Energy analysis and optimization of main hydraulic system in 10,000 kN fine blanking press with simulation and experimental methods

In this paper, a low-high pressure double oil hydraulic system with accumulators was presented with the features of high working efficiency, high control precision and large working capacity. To analyze the hydraulic system energy characteristic, a novel analytical approach, based on the mathematical energy dissipation model of hydraulic components, was proposed to calculate the system energy dissipation by establishing high accuracy simulation model. A test rig with a 10,000 kN hydraulic fine blanking press was built up and used to validate the proposed system and the energy analytical approach. Finally, the system energy dissipation of the 10,000 kN hydraulic fine blanking press was analyzed and the pump output pressure was optimized to minimize the energy dissipation with the genetic algorithm. Results indicate that the energy efficiency of the hydraulic fine blanking press hydraulic system is low, and especially under low-load conditions it is (0–50% full load rate) less than 15%. About 50% of the total input energy is consumed in the form of valve dissipation resulted from the imbalance of installed and demanded energy. After optimization, the total input energy decreases by nearly 50% and the energy efficiency increases by 10%, especially under low-load conditions.

The Influence of Valve-Pump Weight Ratios on the Dynamic Response of Leaking Valve-Pump Parallel Control Hydraulic Systems

A new leaking valve-pump parallel control (LVPC) oil hydraulic system is proposed to improve the performance of dynamic response of present variable speed pump control (VSPC) system, which is an oil hydraulic control system with saving energy. In the LVPC, a control valve is operating at leaking status, together with a variable speed pump, to regulate the system flow of hydraulic oil simultaneously. Therefore, the degree of valve control and pump control can be adjusted by regulating the valve-pump weight ratio. The LVPC system design, mathematical model development, system parameter and control performance analysis are carried out systematically followed by an experimental for validation process. Results have shown that after introducing the valve control, the total leakage coefficient increases significantly over a wide range with the operating point and this further increases damping ratios and reduces the velocity stiffness. As the valve-pump weight ratio determines the flow distribution between the valve and the pump and the weight factors of the valve and/or the pump controls determines the response speed of the LVPC system, thus if the weight factors are constrained properly, the LVPC system will eventually have a large synthetic open-loop gain and it will respond faster than the VSPC system. The LVPC will enrich the control schemes of oil hydraulic system and has potential value in application requiring of fast response.

Energy Efficiency Improvement of Water Hydraulic Motor System with Reducing Pump Supply Pressure

Water hydraulic systems are an outstanding driving source because they have no risk of environmental pollution and fire hazard. However, conventional water hydraulic systems, as well as oil hydraulic systems, have larger energy loss for pressure loss through mainly control valves. Here, there are two solutions to achieve the energy-saving: reducing the restriction loss through control valves, and applying the energy recovery module with an accumulator. In oil hydraulic systems, the independent metering system which includes two control valves for one actuator to reduce the restriction loss through valves has been proposed. This system applies a variable displacement pump to control the pump supply flow. However, variable displacement pumps have been still at the stage of research and development in the field of water hydraulics because of the internal leakage and the difficulty of selecting materials on sliding parts. In contrast, the energy recovery module can reduce the energy consumption and be applied to water hydraulic systems.

A numerical investigation in characteristics of flow force under cavitation state inside the water hydraulic poppet valves

Compared with the oil hydraulic systems, cavitation is more serious in water hydraulic systems due to the higher saturated vapor pressure of water. Poppet valve is one of important hydraulic components and cavitation is easy to happen due to the sharp pressure drop caused by throttling. This paper presents a numerical investigation into the flow force and cavitation characteristics inside water hydraulic poppet valves. Three kinds of typical structures of poppet valves are selected in the research. The effects of geometric parameters and backpressure of the poppet valves on flow characteristics, cavitation and flow force have been analyzed. Considering the axisymmetric structure of the valves, a half of 2D mixture model is selected and a two-phase mixture model is adopted in the calculation. The accuracy of the numerical models has been validated by comparing the simulation results with the experiment data. The results reveal that two-stage throttle valve (TS valve) can effectively suppress the occurrence of cavitation while the flow force of TS valve is much bigger than that of other valves. By comparing the simulation results under two different boundary conditions (including with backpressure and without backpressure), it seems that cavitation could slightly decrease the flow force.

Development of Component to Reduce Pressure Pulsation in Oil-hydraulic System

Development of Component to Reduce Pressure Pulsation in Oil-hydraulic System

Optimal Design of a Servo Motor for Energy-Saving in Oil Hydraulic System of Machine Tools

This paper presents a permanent magnet synchronous serve motor (PMSSM) to replace an induction motor (IM) in the oil hydraulic system in machine tools to drive a pump for supplying the oil. The proposed is designed to meet not only the machine performance, such as higher average torque per volume of magnet usage and the efficiency, and lower torque ripple, but also the energy-saving policy. The motor is optimized using the fuzzy-based Taguchi method. Finally, the proposed motor is installed in the machine tools for measurement, and compared with the tradition machine tools installed with IM.

Cavitation in a hydraulic system: The influence of the distributor geometry on cavitation inception and study of the interactions between bubbles

Hydraulic systems are often subjected to pressure drops, which may lead to cavitation. In systems such as power steering, hoist loads, or ventricular assist devices, distributors are generally used. Significant pressure losses can happen in a distributor due to gap and overlap, which may lead to cavitation development. However, this issue is almost never included in the conception of the distributors. In this study, the multibubble model of the modified Rayleigh–Plesset equation is applied to the rotary distributor of an oil hydraulic system. The influence of the overlap length, the gap, the rotation speed, and distributor inlet pressure on the cavitation and particularly the interactions between bubbles at cavitation inception are studied. The study highlights a critical length of the overlap; over this value, the overlap length influences significantly the cavitation duration and the void fraction. More generally, some geometrical details have a strong influence on cavitation. Optimization of these details in engine parts, taking account the occurrence of cavitation, would be an appropriate solution to reduce its effects. The study also demonstrates that the growth of small bubbles may be delayed by the interactions with the nearby bigger ones, even if the ambient pressure is lower than their theoretical critical pressure. They eventually collapse at the first moments of the cavitation development. However, if the ambient pressure drops further, that is, beyond a critical pressure, a small bubble gains enough inertial energy to overcome these interaction phenomena and thus to grow. The growth of small bubbles increases the interactions between bubbles and slows down the growth of nearby bigger ones. The results show that the interactions between bubbles are of primary importance in the first moments of the cavitation development, which suggests that they should be taken into account in the definition of the critical pressure.

アキュムレータを用いたアイドリングストップ方式による油圧源の省エネルギー

Recently, energy saving is very important because the environmental contamination and the shortage of energy resources have become a major problem in a number of fields including oil hydraulic systems. We previously proposed a pump unit driven by an electric motor with intermittent operation. This pump unit achieves electrical energy saving compared with conventional pump units under a wide range of driving condition. However, construction machines and vehicles mainly use an engine as a power source. In this study, we test the intermittent operation of a pump unit driven by an engine, and we achieve automatic engine restart by means of a hydraulic assist. We research an intermittently operated pump unit driven by a gasoline engine and achieve a saving in energy. In addition, we research the effect of accumulator volume and the stability of the engine restart.

J0540305 風力利用を想定した油圧式発熱システムの開発([J054-03]再生可能エネルギー(3))

The purposes of this study are to clarify the validity of the conversion of wind power into thermal energy by using the hydraulic heating system and to consider the optimal method of this system. An oil pump was driven by a DC-motor instead of wind turbine, and the oil increased in temperature by the pressure loss of orifices mounted in a heating element connected to the hydraulic circuit. The power consumed by pressure loss, the effective heating rate, and the oil temperature increase process were measured under several different conditions, for example the number of orifice plates and the space between its plates. As the results of these investigations, it was found that this oil hydraulic heating system using the pressure loss of orifices worked well for the wind power heater.

Finite element analysis of proportional solenoid characteristics in hydraulic valves

Proportional hydraulic valves (PHVs) have remarkable applications in different branches of industry. These valves can control an oil hydraulic system. One of the most important factors affecting a proportional solenoid (PS) is the geometry that affects its magnetic force with respect to its plunger position. Other effective factors include the size of the air gap, the current density and various soft magnetic materials that have different B-H (flux density versus field intensity) curves. Electromagnetic analysis (EMA) is used to enhance the reliability and accuracy of the PS and to reduce the total cost. In this paper, a range of PSs are software package with different air gaps, dimensional parameters, current densities and soft magnetic materials. The magnetic flux density and force are calculated using a finite element method (FEM), and the results are compared with the experimental results of an actual PS.

Proposal of a Mechanism to Restrict Pressure Change by Oil Temperature Change

One of the advantages of an oil-hydraulic system is that it keeps the value of its oil pressure when the pressurized oil is enclosed in a container. However, when the temperature of the oil changes, it is impossible to keep the value. If a pressure-control sub-system is used to prevent the pressure change, the whole system becomes complicated. In addition, energy is consumed when the pressure is adjusted by the quantity of oil flowing in or out of the container. From these view points, it would be useful if a component were developed which prevented the pressure change caused by the change in oil temperature without controlling the quantity of oil. Therefore, in this paper, a mechanism to prevent the pressure change caused by the oil temperature change is proposed to secure the advantages of the oil hydraulic system even when the temperature of the oil changes. And a component is fabricated to investigate the validity of the proposed mechanism. Its validity is investigated experimentally when the temperature of the oil increases and when the temperature of the oil decreases after it increases.